Field of the Invention
The present invention relates to a sheet conveying device and an image forming apparatus, and more particularly, to a sheet conveying device and an image forming apparatus in which a conveying unit that conveys a sheet and a sheet discharge roller are driven using the same motor.
Description of the Related Art
A sheet conveying device is used in an image forming apparatus or the like, for example, to convey a sheet on which an image is formed. Examples of the image forming apparatus which uses such a sheet conveying device include a multi-function peripheral (MFP) having a scanner function, a facsimile function, a copier function, a printer function, a data communication function, and a server function, a fax, a copier, and a printer.
In an apparatus which uses a sheet conveying device, it is necessary to rotate a sheet conveying roller at a high speed in order to increase the number of sheets conveyed per unit time and to secure high productivity. However, when the roller rotates at a high speed, sheets are discharged to a sheet discharge tray at a high speed by a sheet discharge roller, and the stackability of sheets discharged onto the sheet discharge tray deteriorates (the sheets on the sheet discharge tray become ill-ordered).
To solve this problem, an example in which a sheet discharge roller is driven using a motor different from a motor that drives a conveying roller, and a rotation speed of the sheet discharge roller is decreased only before sheets are discharged so that high productivity and satisfactory stackability can be secured (for example, see JP 4404876 B2 and JP 2004-333634 A).
However, in such a configuration as illustrated in JP 4404876 B2 and JP 2004-333634 A, since another motor for driving the sheet discharge roller is used to decrease the rotation speed of the sheet discharge roller only during discharging, power consumption increases and the manufacturing cost increases.
In order to achieve high productivity, satisfactory stackability, and low power consumption, it is necessary to share the motor for driving the sheet discharge roller and the motor for driving another conveying roller. For example, it is necessary to eliminate a sheet discharge motor and to use a motor close to the sheet discharge roller as a driving source of the sheet discharge motor. However, when the sheet discharge roller is driven using a motor that drives another conveying roller, the stackability may deteriorate if high productivity is to be secured without decreasing the rotation speed of another conveying roller. That is, another conveying roller and the sheet discharge roller rotate at a constant speed for conveying sheets and the sheets are discharged forcefully.